In the past gaskets have been employed in various fields of art to seal parts compressed together to prevent fluid leakage between the parts.
One such usage is in compressor valve plates used in air conditioners where the gasket under pressure is required to be a specific thickness in the order of 0.025 inch within strict tolerances of plus or minus 0.0005 inch under load to prevent fluid leakage and consequent loss of efficiency and damage to various parts. The gaskets employed are subjected to rigid and laborious testing procedures to ensure strict adherence to specified thicknesses under the load to be employed which may be well upwards of 1,000 PSI.
In the manufacturing process in obtaining the gaskets, wide rolls of gasket material are conventionally slit into narrower rolls of a width suitable for stamping out gaskets. Such wide rolls can vary in thickness across the width of the wide roll and in the length of the roll as it comes from the manufacturer of the roll. This is due to difficulty in quality control to meet the specific thickness requirements of certain gaskets.
To meet the specifications required for example, in the compressor industry, the manufacturer of gaskets of 0.025 inch which compress under load for example to 0.021 inch, must supply a gasket of that thickness plus or minus 0.0005 inch. To meet this requirement, each manufactured gasket is tested, for example, at 2500 PSI to determine whether the thickness is at the designated load 0.021 inch plus or minus 0.0005.
The quality control problem requires a laborious and time consuming effort which has been necessary where exact specifications are required for high quality gaskets.